Download - 5 Chromosomes
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Chromosomes
Basic makeup of a chromosome
.
1. DNA (deoxyribose nucleic acid)
2. Protein Histone
This complex of DNA and Protein is called
Chromatin
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Chromosome Structure
chromosomes (enhances
stability)
Centromere: It bindsCentromere
e c roma s oge er
Chromatids: two halves
of each chromosome. Chromatids or Sister chromatids
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Chromosomes classification
Homologous Chromosomes
These are identical chromosomes that exist in airsin diploid organisms
Identical gene location and centromere placement
Different alleles
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Locus for
flower color
genes
Homologous
pair of
chromosomes
Allele w Allele W
chromosomes are
of a single
chromatids and at
other times consisto
matids
One chromosome One chromosome
of two chromatids
Twoch
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Chromatids
only during mitosis or meiosis.
Identical gene location and centromere
placement
Identical allele before crossover
Human Male Karyotype
Homologous chromosomes
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Human Karyotype during metaphase
Homologous Chromosomes
Sister Chromatids
Chromosomes
Species Sci. Name 2n n
Cattle Bos taurus 60 30
Dog Canis familiaris 78 39
Horse Equus caballus 64 32
Human Homo sapiens 46 23
Black bread mold Aspergillus nidulans 16 8
Tobacco Nicotiana tabacum 48 24
Maize Zea mays 20 10
Soybean Glycine max 40 20
Cotton Gossypium hirsutum 52 26
Wheat Triticum aestivum 42 21
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Why is it impossible for
organism from different
genera to reproduce?
Polyploidy
Presence of more than two sets ofchromosomes
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Most eukaryotic organisms are haploid
-chromosomes
Human = 2n (n = 23) = 46
Homologous chromosomes present
-chromosomes
Human = n = 23No homologous chromosomes
Mutations based on
chromosome number
Aneuploidy change in the number of individual
Polyploidy- change in the number of chromosome sets
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Aneupolidy
Animals
Aneupoloidy typically alter the phenotypedrastically and are commonly lethal in animalsand plants.
of all spontaneous abortions (miscarry), withaneuploidy accounting for most of them.
Only 2% of fetus with aneuploidy survive
Down Syndrome
trisomoy in humans.
Trisomy of chromosome 21
Frequency = 1:800 births
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Down Syndrome
Down Syndrome
Conditions
Very similar amongindividuals
Round heads and flatfaces
Short
Retarded physicaland mentaldevelopment
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Down Syndrome
1:1000 at 30
1:100 at 40
Other Trisomy in humans
Severe retardation
Most die at age of 1
Trisom 13 Patau s ndroms 90% die before age 3
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Aneuploidy
Plants
Has been observed in some
plants
x Tobacco
x ven ng pr mrose
x Jimson weed
Trisomy
Jimson weed =
x 12 trisomicconditions have
been observedx Each changes alters
the phenotype
Rice Trisomic for the
longer chromosomesgrow slower
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Polyploidy
Autopoloidy all chromosome sets are from singlespec es
Allopolyploidy chromosome sets are from two ormore species
Polyploidy
,and pentaploids (5n).
40% of flowering plants and 70 to 80% ofgrasses are polyploids
Wheat, oats, cotton, potato, and sugar cane arepolyploids
No birds
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Autopolyploidy
Ex. No cell division of 2n organism in
mitosis
Autotriploid = 3n
Ex. No cell division after Meiosis II and fuse
with haploid gamete
Autopolyploidy
2n = 22
3n =33
Watermelon
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Allopolyploidy
P1 ABC P2 GHI
F1 = ABCGHI - sterile
xNo chromosome pairs
x are y ave no ce v s on n m os s anproduce viable seed
xAllotetraploid = AABBCCGGHHIINormal gametes
What is purpose of ployploidy
thus many polyploids are larger than diploids.
Potato autopolyploid 4n 48
Peanut Autopolyploid 4n 40
Sweet otato Auto ol loid 6n 90
Tobacco Allopolyploid 4n 48
Cotton Allopolyploid 4n 52
Wheat Allopolyploid 6n 42
Strawberry Allopolyploid 8n 56